By Joseph Ax

(Reuters) -A Republican plan to redraw congressional lines in Texas at U.S. President Donald Trump’s urging threatens to launch an all-out national redistricting war, with both Republican and Democratic states considering whether to redraw their own maps.

The outcome could determine whether Republicans maintain control of the U.S. House of Representatives in the November 2026 midterm elections. Republicans currently hold a narrow 219-212 majority, with four vacancies.

While redistricting must occur every 10 years to incorporate U.S. Census data, redrawing maps in the middle of the decade has historically been exceedingly rare. Republicans, who control more state governments than Democrats, appear poised to pick up a half-dozen seats or more.

The practice of gerrymandering – drawing district lines to benefit one party over another – has contributed to a decline in the number of competitive House seats. Only about three dozen districts out of 435 are seen as competitive by nonpartisan analysts as of August.

Here is how the process could unfold in Republican-controlled and Democratic-controlled states.

REPUBLICAN-CONTROLLED STATES

TEXAS

Republican legislators have unveiled a map aimed at flipping five Democratic seats. More than 50 Democratic lawmakers left the state in early August, denying the state House of Representatives a quorum and preventing a vote on the map, at least for now. Governor Greg Abbott has threatened the absent Democrats with arrest and removal from office, though legal experts have questioned whether those threats can be carried out. Republicans already control 25 of the state’s 38 seats under a Republican-drawn map from 2021.

OHIO

An unusual state law requires the Republican-dominated legislature to pass a new map for 2026, because the previous one, drawn in 2021, was approved with no Democratic votes. Republicans, who already control 10 of the state’s 15 seats, could target two or even three Democrats with a new map.

FLORIDA

Republican Florida House Speaker Daniel Perez has called for a select committee to work on congressional redistricting, and Republican Governor Ron DeSantis has signaled he would support the effort. A new map could target two or three Democrats. Republicans already control 20 of the state’s 28 seats, thanks to an aggressive map DeSantis pushed through the legislature in 2021 that flipped four Democratic seats in 2022.

One possible legal hurdle is a constitutional amendment, approved by voters in 2010, that bars the legislature from drawing districts purely for partisan gain. The Florida Supreme Court, which upheld DeSantis’ 2021 map, is entirely Republican-appointed, and four of the seven justices were nominated by DeSantis.

INDIANA

The White House has pressured Indiana Republicans to consider redistricting. Republicans control seven of the state’s nine congressional seats and could easily target one Democratic incumbent.

MISSOURI

Republican Governor Mike Kehoe and Republican lawmakers have expressed openness to drawing a new map that would likely target Democratic U.S. Representative Emanuel Cleaver’s Kansas City-based seat. Flipping his district would give Republicans control of six of the state’s seven seats.

DEMOCRATIC-CONTROLLED STATES

CALIFORNIA

Governor Gavin Newsom has vowed to pursue a new congressional map if Texas Republicans follow through on their redistricting plan. Democratic legislators are already considering a map that would seek to flip five Republican seats while shoring up vulnerable Democratic incumbents. Democrats currently control 43 of the state’s 52 districts.

A new map would require Democrats to pull off a complicated legal two-step. California uses an independent commission to draw congressional lines. Newsom has said he would call for a special election in November asking voters to give lawmakers the power to draw maps until the commission takes over again following the 2030 U.S. Census. There are no statewide elections in California this year, which could make turnout a wild card.

ILLINOIS

Democratic Governor JB Pritzker has suggested his party would consider redrawing its congressional districts in response to Texas. But Illinois already has what is considered one of the most gerrymandered maps in the country, with Democrats controlling 14 of the state’s 17 seats. Flipping even one Republican seat could prove challenging.

MARYLAND

The Democratic majority leader of the state House, David Moon, has introduced legislation to re-open congressional redistricting if any other state – such as Texas – does so. Democrats already control seven of the state’s eight districts, so any new map could at best flip a single seat. Redistricting could also face legal hurdles: the party attempted to install an 8-0 map in 2022, but a state judge struck it down as unconstitutionally gerrymandered.

NEW YORK

Democratic Governor Kathy Hochul has vowed to pursue redistricting if Texas approves a new map, but legal constraints likely make that impossible until 2028. Voters would have to approve a constitutional amendment to permit mid-decade redistricting, and under state law such an amendment cannot be put on the ballot before 2027. Democrats hold 19 of the state’s 26 seats after a more aggressive gerrymander in 2022 was blocked by the courts.

(Reporting by Joseph Ax, additional reporting by Andy Sullivan: Editing by Scott Malone and Nia Williams)